Touch input device for computer interface input and display is normally activated or operated by detecting touching or proximity presence of user's finger or sharp end of a stylus. The touching typically requires to push sensing surface of the device with certain force to activate a valid detection. The proximity presence does not require to touch or push the device surface, but may require touching end of finger or stylus capable of interfering sensing filed of the device in proximity. For example, for capacitive sensing or inductance sensing, dry skin of finger may not cause sufficient disturbance to sensing electrical field, thus causing irresponsive to presence of the finger on the sensing surface. If touching end of stylus is made of electrical insulation material, it will not interfere with sensing electrical field to activate a valid detection. Such problem may be solved by wearing a conductive cover on finger or making touching end of stylus of conductive material. During operation, touching with certain force may scratch the sensing surface to induce system failure after long term use or smear displayed image for touch display application due to either scratching or contamination. Anti-scratching coating may be put on top of the sensing surface to alleviate the scratching problem. Although not having scratching issue, proximity presence sensing often experiences false detection or inaccurate position measurement of input. Using specially made stylus may dramatically improve detection reliability and accuracy. However, due to nature of proximity sensing, measurement accuracy of input position is limited. Both touching detection and proximity presence detection don't work if input objective such as finger or stylus is placed not very close to the sensing surface. So, remote operation is not feasible for commonly used touch input device.
A type of input device may detect a light beam upon its sensing surface, similar as a touch input using finger or stylus. Such type of input device previously uses a photodetector array made on a substrate to detect position of the incidence light beam. The light beam is normally sent out by a light pointer or a light pen or light stylus. The light pointer or a light pen does not have to be placed in proximity to the sensing surface. Thus, the type of input device may be operated remotely as far as the light beam incidences sufficient light intensity to activate the photodetectors. Such remote operation is not possible for touch input devices such as resistive type, capacitive type, inductive type, or other proximity sensing type. This remote operation capability is desired by remote control of user interface for computer driven large size flat panel display or large size flat panel display TV. In these applications, user may sit or stand several meters away from the display and perform all kinds of user interface operation, for example, internet related operation such as web surfacing, message checking, multimedia playing and so on. However, cost of making photodetector array and related control electronics is very high. The cost issue becomes worse when size of display increases, thus causing a dilemma that large size display calls out need of the remote operation but it is more unlikely to get that made under a reasonable penalty of cost increase. Within foreseeable future, unless integration of photodetector array with image pixels of flat panel display achieves a significant breakthrough, it is not practical to make such type of input device price/benefit competitive to touch input device and justify its cost incurred for adding the functionality.
Therefore, low cost input device working conjunctively with a light pointer or a light pen is demanded for non-touching and remote operation of computer based user interface or similar uses.
The information disclosed in this Background of the Invention section is only for the enhancement of understanding of the background of the invention, and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.